Design of Flexible and Rigid Pavement: A Review

Flexible pavements are widely used despite some doubts regarding their economics under different conditions. Two most important parameters that govern the pavement design are soil sub-grade and traffic loading. The Indian guidelines for the design of flexible pavements use soil sub-grade strength in terms of California Bearing Ratio (CBR) and traffic loading in terms of million standard axles (msa). For the design of rigid pavements, IRC: 58-2002 uses the same parameters in terms of modulus of sub-grade reaction, k, and axle load distribution (ALD). To compare the cost of two types of pavements, it is necessary to ensure that they are designed for the same traffic loading. Therefore, a study was done to convert the traffic load given in msa into ALD and vice-versa. Mathematical models are developed to estimate the ALD from individual vehicle counts. Mathematical expressions are developed to relate the cost of pavements with soil CBR and traffic in msa. The critical line of equal costs on the plane of CBR versus msa is also identified. This is a swing line which delineates the economic feasibility of two types of pavements